Polyurethane-based adhesives, systems for such adhesives, articles therefrom, and methods of making

Abstract

Polyurethane-based adhesives of the invention comprise the reaction product of: an isocyanate-reactive component comprising at least two isocyanate-reactive materials, the at least two isocyanate-reactive materials comprising a first isocyanate-reactive material having a weight average molecular weight of less than 2,000 and a second isocyanate-reactive material having a weight average molecular weight of 2,000 or more; an isocyanate-functional component; an optional reactive emulsifying compound; and an optional chain extending agent. The adhesives, which are preferably pressure-sensitive adhesives, can be prepared from 100% solids, waterborne or solventborne systems.

What is claimed is:  
     
       1. A polyurethane-based pressure-sensitive adhesive prepared from a waterborne system, the adhesive comprising the reaction product of: 
       an isocyanate-reactive component comprising at least two isocyanate-reactive materials, the at least two isocyanate-reactive materials comprising:  
       a first isocyanate-reactive material comprising a polyol and having a weight average molecular weight of less than 2,000, and  
       a second isocyanate-reactive material comprising a polyol and having a weight average molecular weight of 2,000 or more;  
       wherein the second isocyanate-reactive material comprises a majority of the isocyanate-reactive component based on total weight of the isocyanate-reactive component; 
       an isocyanate-functional component;  
       an optional reactive emulsifying compound; and  
       an optional chain extending agent.  
     
     
       2. The polyurethane-based pressure-sensitive adhesive of  claim 1 , wherein the isocyanate-reactive component comprises at least one polyol. 
     
     
       3. The polyurethane-based pressure-sensitive adhesive of  claim 1 , wherein the first and second isocyanate-reactive materials are diols. 
     
     
       4. The polyurethane-based pressure-sensitive adhesive of  claim 1 , wherein the isocyanate-reactive component comprises at least one polyoxyalkylene polyol. 
     
     
       5. The polyurethane-based pressure-sensitive adhesive of  claim 1 , wherein at least one of the first and second isocyanate-reactive materials comprises less than about 8% by weight monols. 
     
     
       6. The polyurethane-based pressure-sensitive adhesive of  claim 1 , wherein at least one of the first and second isocyanate-reactive materials is a polyol having a ratio of polyol molecular weight to weight % monol of at least about 800. 
     
     
       7. The polyurethane-based pressure-sensitive adhesive of  claim 1 , wherein the first isocyanate-reactive material has a weight average molecular weight of less than about 1,800. 
     
     
       8. The polyurethane-based pressure-sensitive adhesive of  claim 1 , wherein the first isocyanate-reactive material has a weight average molecular weight of less than about 1,600. 
     
     
       9. The polyurethane-based pressure-sensitive adhesive of  claim 1 , wherein the first isocyanate-reactive material has a weight average molecular weight of less than about 1,000. 
     
     
       10. The polyurethane-based pressure-sensitive adhesive of  claim 1 , wherein the second isocyanate-reactive material has a weight average molecular weight of greater than about 2,500. 
     
     
       11. The polyurethane-based pressure-sensitive adhesive of  claim 1 , wherein the second isocyanate-reactive material has a weight average molecular weight of greater than about 3,000. 
     
     
       12. The polyurethane-based pressure-sensitive adhesive of  claim 1 , wherein the second isocyanate-reactive material has a weight average molecular weight of greater than about 3,500. 
     
     
       13. The polyurethane-based pressure-sensitive adhesive of  claim 1 , wherein the second isocyanate-reactive material has a weight average molecular weight of greater than about 6,000. 
     
     
       14. The polyurethane-based pressure-sensitive adhesive of  claim 1 , wherein the weight average molecular weights of the first and second isocyanate-reactive materials differ by at least about 500. 
     
     
       15. The polyurethane-based pressure-sensitive adhesive of  claim 1 , wherein the weight average molecular weights of the first and second isocyanate-reactive materials differ by at least about 1,000. 
     
     
       16. The polyurethane-based pressure-sensitive adhesive of  claim 1 , wherein the weight average molecular weights of the first and second isocyanate-reactive materials differ by at least about 1,500. 
     
     
       17. The polyurethane-based pressure-sensitive adhesive of  claim 1 , wherein the weight average molecular weights of the first and second isocyanate-reactive materials differ by at least about 2,000. 
     
     
       18. The polyurethane-based pressure-sensitive adhesive of  claim 1 , wherein the weight average molecular weights of the first and second isocyanate-reactive materials differ by at least about 2,500. 
     
     
       19. The polyurethane-based pressure-sensitive adhesive of  claim 1 , wherein the first isocyanate-reactive material comprises about 1 to about 40 percent by weight of the isocyanate-reactive material component and the second isocyanate-reactive material comprises about 60 to about 99 percent by weight of the isocyanate-reactive material component. 
     
     
       20. The polyurethane-based pressure-sensitive adhesive of  claim 1 , wherein the first isocyanate-reactive material comprises about 5 to about 25 percent by weight of the isocyanate-reactive material component and the second isocyanate-reactive material comprises about 75 to about 95 percent by weight of the isocyanate-reactive material component. 
     
     
       21. The polyurethane-based pressure-sensitive adhesive of  claim 1 , wherein the isocyanate-functional component comprises a diisocyanate. 
     
     
       22. The polyurethane-based pressure-sensitive adhesive of  claim 1 , wherein the reactive emulsifying compound comprises at least about 0.5% by weight of the total reactants. 
     
     
       23. The polyurethane-based pressure-sensitive adhesive of  claim 1 , wherein the isocyanate-reactive material component comprises less than about 10% by weight of polyols other than diols. 
     
     
       24. The polyurethane-based pressure-sensitive adhesive of  claim 1 , wherein the isocyanate-reactive material component comprises less than about 5% by weight of polyols other than diols. 
     
     
       25. The polyurethane-based pressure-sensitive adhesive of  claim 1 , wherein the adhesive is prepared from a poly(urethane-urea) aqueous dispersion. 
     
     
       26. The polyurethane-based pressure-sensitive adhesive of  claim 1 , wherein polyurethane-based pressure-sensitive adhesive further comprises the reaction product of a chain extending agent. 
     
     
       27. A substrate at least partially coated with the polyurethane-based pressure-sensitive adhesive of  claim 1 . 
     
     
       28. A tape comprising: 
       a backing having a first and second side; and  
       the pressure-sensitive adhesive of  claim 1  coated on at least a portion of the first side of the backing and, optionally, on at least a portion of the second side of the backing.  
     
     
       29. A method of preparing a polyurethane-based pressure-sensitive adhesive comprising the steps of: 
       providing an isocyanate-reactive component comprising at least two isocyanate-reactive materials, a first isocyanate-reactive material comprising a polyol and having a weight average molecular weight of less than 2,000 and a second isocyanate-reactive material comprising a polyol and having a weight average molecular weight of 2,000 or more, wherein the second isocyanate-reactive material comprises a majority of the isocyanate-reactive component based on total weight of the isocyanate-reactive component;  
       providing an isocyanate-functional component;  
       optionally providing a reactive emulsifying compound;  
       allowing the isocyanate-reactive component, the isocyanate-functional component, and the optional reactive emulsifying compound to react to form a polyurethrane prepolymer; and  
       chain extending the polyurethane prepolymer.  
     
     
       30. The method of  claim 29 , further comprising the step of dispersing the polyurethane prepolymer in an aqueous dispersing medium. 
     
     
       31. The method of  claim 30 , further comprising the step of drying the aqueous dispersing medium to form a coating of the polyurethane-based pressure sensitive adhesive. 
     
     
       32. A polyurethane-based pressure-sensitive adhesive dispersion comprising the reaction product of: 
       an isocyanate-reactive component comprising at least two isocyanate-reactive materials, the at least two isocyanate-reactive materials comprising:  
       a first isocyanate-reactive material comprising a polyol and having a weight average molecular weight of less than 2,000, and  
       a second isocyanate-reactive material comprising a polyol and having a weight average molecular weight of 2,000 or more;  
       wherein the second isocyanate-reactive material comprises a majority of the isocyanate-reactive component based on total weight of the isocyanate-reactive component; 
       an isocyanate-functional component;  
       an optional reactive emulsifying compound; and  
       an optional chain extending agent,  
       wherein the reaction product is dispersed in an aqueous dispersing medium. 
     
     
       33. A polyurethane-based pressure-sensitive adhesive solution comprising the reaction product of: 
       an isocyanate-reactive component comprising at least two isocyanate-reactive materials, the at least two isocyanate-reactive materials comprising:  
       a first isocyanate-reactive material comprising a polyol and having a weight average molecular weight of less than 2,000, and  
       a second isocyanate-reactive material comprising a polyol and having a weight average molecular weight of 2,000 or more;  
       wherein the second isocyanate-reactive material comprises a majority of the isocyanate-reactive component based on total weight of the isocyanate-reactive component; 
       an isocyanate-functional component;  
       an optional reactive emulsifying compound; and  
       an optional chain extending agent,  
       wherein the reaction product is solvated in a solvating medium. 
     
     
       34. A polyurethane-based adhesive prepared from a waterborne system, the adhesive comprising the reaction product of: 
       an isocyanate-reactive component comprising at least two isocyanate-reactive materials, the at least two isocyanate-reactive materials comprising;  
       a first isocyanate-reactive material comprising a polyol and having a weight average molecular weight of greater than 400 to less than 2,000, and  
       a second isocyanate-reactive material comprising a polyol and having a weight average molecular weight of 2,000 or more;  
       wherein the second isocyanate-reactive material comprises a majority of the isocyanate-reactive component based on total weight of the isocyanate-reactive component; 
       an isocyanate-functional component;  
       an optional reactive emulsifying compound; and  
       an optional chain extending agent.  
     
     
       35. A substrate at least partially coated with the polyurethane-based adhesive of  claim 34 .